diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f0aa029..aefbf9c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         ruby:
-          - 2.7.3
+          - 3.0.7
           - 3.1.3
     steps:
     - uses: actions/checkout@v2
diff --git a/markdiff.gemspec b/markdiff.gemspec
index b3fd95a..b7beb56 100644
--- a/markdiff.gemspec
+++ b/markdiff.gemspec
@@ -13,6 +13,8 @@ Gem::Specification.new do |spec|
   spec.files         = `git ls-files -z`.split("\x0").reject { |f| f.start_with?("spec/") }
   spec.require_paths = ["lib"]
 
+  spec.required_ruby_version = ">= 3"
+
   spec.add_development_dependency "bundler"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "redcarpet"